The present invention relates to the field of fiber optic cables and more specifically to efficient high-fiber count ribbon stack packaging configurations having corner cushions to avoid contact between corner fibers and a buffer tube wall thus reducing attenuation problems.
Fiber optic cables enable communication networks to operate with wide bandwidth and low noise operation. As communication technologies and data transmission mediums evolve, there is an increasing demand for fiber optic cables with greater bandwidth and minimal distortion. Manufacturers of optical cables attempt to satisfy these demands through innovative fiber optic designs. In doing so, numerous factors must be considered to produce an optimal and functional cable.
For example, packing configurations of fiber ribbon stacks within the buffer tube affects the diameter, weight and cost of the buffer tube and ultimately the fiber optic cable. Therefore, efficient packaging configurations for cables, containing high-fiber count ribbon stacks, are continuously tested.
Similarly, while attempting to achieve an optimal high-fiber count ribbon stack configuration and reduced cable diameter, a manufacture may also attempt to minimize attenuation problems. A buffer tube typically houses a fiber ribbon stack configuration. Often times, the fiber ribbon stack is loosely housed within the buffer tube thus allowing the ribbon stack to move within the buffer tube. Attenuation problems occur when the corner fibers of the ribbon stack contact the buffer tube walls. Typically, such contact may be due to bending of the buffer tube, transverse compression of the tube, or contraction of the tube due cold temperatures or elongation of the tube due to tension. Attenuation results in transmission loss. Thus, decreasing attenuation within a buffer tube will increase the overall performance of the fiber optic cable.
Currently, the existing art fails to take into account the need for stabilization among high-fiber count ribbon stacks in order to decrease attenuation problems. Furthermore, the prior art fails to provide an optimal packaging configuration for high-fiber count ribbon stacks. Therefore, it would be desirable to design an optimal packaging configuration for ribbon stacks having a high-fiber count such that the number of fibers per unit square area of the buffer tube cross-section increases, while minimizing attenuation problems and the overall cable diameter.
The present invention solves the above described problems by providing a high-fiber count ribbon cable having improved mechanical and optical performance, in addition to a reduced overall cable diameter and cable weight. Specifically, the present invention discloses an efficient packaging configuration using 12-fiber ribbons and 24-fiber ribbons to formulate a high-fiber count ribbon stack while utilizing cushions to fill the empty spaces of the buffer tube that houses the ribbon stack. The cushions enable the ribbon stack to center itself within the tube thereby decreasing attenuation problems.
The optimal and efficient packaging configurations of the present invention is achieved through multi-parametric optimization that includes numerous buffer tubes and ribbon stack configurations composed of high-fiber count ribbons, such as 12-count fiber ribbons and 24-count fiber ribbons. Specifically, an optimal geometric analysis is performed on fiber optic cables utilizing one to six buffer tubes per cable and having central and stranded tube designs to identify optimal buffer tube configurations and to reduce the overall diameter of the fiber optic cable. Furthermore, parametric criteria used to configure the optimal packaging and high-fiber count ribbon stack designs includes, but is not limited to, minimizing the ribbon stack size (in the diagonal direction), maximizing the fiber count and stack stability, minimizing the number of structural components and minimizing the overall cable diameter. In all, two ribbon stack configurations utilizing parallel lying and perpendicular lying fiber ribbons achieve the above-mentioned goals
In an embodiment of the invention, a high-fiber count ribbon stack, having a square shape configuration, is provided. Specifically, fiber ribbons are stacked on top of one another in the parallel direction creating a vertical fiber ribbon stack. Once the vertical stack of parallel lying fiber ribbons is formed, two additional stacks of fiber ribbons are attached to a first and second side of the vertical stack in a perpendicular direction. Coupling the perpendicular lying ribbon stacks to the vertical lying ribbon stack results in a ribbon stack substantially square in shape. The square shaped ribbon stack configuration fits nicely into numerous buffer tubes.
For example, twenty 12-count fiber ribbons may be stacked on top of one another to create a vertical stack. Two additional ribbon stacks, consisting of five 24-count fiber ribbons, may be coupled to each respective side of the vertical stack thereby creating a high-fiber count, square shaped ribbon stack. Accordingly, the total fiber count for this exemplary embodiment is 20xc3x9712+10xc3x9724=480. Because the total fiber count (480) of a cable utilizing the square shaped ribbon stack configuration is divisible by both 12 and 10, the cable may be utilized in both a foreign and domestic market. Such versatility increases the market value of the cable.
Another embodiment of the invention provides for a high-fiber count ribbon stack having a cross-type configuration. Specifically, the cross-type ribbon stack configuration includes parallel lying fiber ribbons stacked on top of one another to create a vertical fiber ribbon stack. Two perpendicular ribbon stacks, composed of high-fiber count ribbons, are attached to each side of the vertical stack in a manner substantially similar to the square shaped ribbon stack configuration. The cross-type ribbon stack, however, further includes two additional perpendicular fiber ribbon stacks coupled to the sides of the above-disclosed square ribbon stack thus resulting in a cross-type configuration.
For example, twenty-four 12-count fiber ribbons may be stacked on top of one another to create a vertical stack. Two additional ribbon stacks, including five 24-count fiber ribbons, may be coupled to each respective side of the vertical stack thereby creating a high-fiber count square shaped ribbon stack. Furthermore, two additional stacks of three 12-fiber ribbons are perpendicularly coupled to the outer edge of the square shaped ribbon stack. Accordingly, the total fiber count for this exemplary cross-type configuration is 24xc3x9712+10xc3x9724+6xc3x9712=600.
In another embodiment of the invention, a cable utilizing an optimal buffer tube arrangement, wherein each buffer tube houses a cross-type ribbon stack configuration, is provided. The 864-fiber count cable utilizes three stranded buffer tubes. The buffer tubes each house a cross-type high-fiber count ribbon stack configuration. The ribbon stack consists of six 24-fiber ribbons. Additional, a first ribbon stack having six 12-fiber ribbons is affixed to the top of the 24-fiber ribbon stack while six 12-fiber ribbons are affixed to the bottom of the 24-fiber ribbon stack.
In yet another embodiment of the invention, cushions may be used to fill the empty and corner spaces between the ribbon stack and the buffer tube walls. The cushions enable the ribbon stack to center itself within the buffer tube and thus protect the ribbon stack edges from contacting the buffer tube walls. The protection provided by the cushions helps decrease attenuation problems.
Another embodiment of the invention provides for an optic unit, or fiber optic cable, having at least one buffer tube, that contains a high-fiber count ribbon stack having a square shape and/or cross-type configuration as described above. Buffer tubes, arranged in numerous configurations and housing a square shape or cross-type ribbon stack configuration, may be utilized to construct a high-fiber count cable. For example, one, two or three buffer tubes, each containing a cross-type and/or square-type ribbon stack configuration may be stranded together to create a cable. In addition, several buffer tubes, housing the high-fiber count ribbon stack configurations, may be placed around a central strength member and stranded together to create a cable. Such arrangements produce a fiber optic cable having a high-fiber count and an overall reduced diameter. Optionally, cushions may be placed between the buffer tube walls and the corners of the fiber ribbon stacks to decrease possible attenuation and to provide the fiber ribbon stacks with a self-centering ability.
In still another embodiment of the invention, a method of manufacturing a high-fiber count buffer tube is provided. The method includes the steps of: creating a vertical ribbon stack by placing twenty 12-count fiber ribbons on top of one another; coupling two ribbon stacks comprising five 24-fiber count ribbons to the edges of the vertical stack in a perpendicular direction to formulate a square fiber ribbon stack having a total fiber count equal to 480; placing cushions between the buffer tube wall and the square ribbon stack corners in order to reduce transmission loss and placing the square ribbon stack in a buffer tube.
The method of manufacturing a high-fiber count buffer tube may further include the step of: creating a vertical ribbon stack using twenty-four 12-count fiber ribbons; creating a third and fourth stack comprising three 12-count fiber ribbons; affixing the third stack, in a perpendicular direction, to a first side of the square ribbon stack; and affixing the fourth stack, in a perpendicular direction, to a second side of the square ribbon stack thereby constructing a cross-type ribbon stack having a total fiber count equal to 600.
In yet another embodiment of the invention, a method of manufacturing a high-fiber count ribbon stack is provided. The method includes the steps of: creating a vertical ribbon stack by placing fiber ribbons on top of one another in a parallel direction; coupling additional ribbon stacks to the edges of the vertical stack in a perpendicular direction to formulate a fiber ribbon stack having a substantially square shape.
The method of manufacturing a high-fiber count ribbon stack may further include the steps of: creating a third and fourth ribbon stack; affixing the third ribbon stack, in a perpendicular direction to a first side of the square stack; and affixing the fourth stack, in a perpendicular direction to a second side of the square stack thereby constructing a cross-type ribbon stack configuration.